1. Field of the Invention
The present invention is broadly concerned with an improved pleating machine permitting rapid, uniform pleating of flexible tubular bodies, such as tubular braided fabric. More particularly, the invention is concerned with such pleating machines, and pleating methods, wherein the machine includes a pair of aligned, tubular pleating jaws together with a drive assembly for generating relative reciprocal movement between the jaws; during jaw movement, the tubular body is successively engaged and uniform pleats are formed.
2. Description of the Prior Art
In the production of certain types of aircraft crew oxygen masks, there is a need for a series of pneumatically expandable tubes which are used as mask harness components. For example, U.S. Patent No. 4,915,106 describes a crew mask of this type, wherein the harness tubes may be inflated to expand the tubes and thus facilitate rapid donning of the mask; once donned, the harness tubes are deflated so that the mask is firmly positioned on the user's head. Such expandable harness tubes are made up of a synthetic resin (e.g., silicone rubber) central tube surrounded by a braided fabric such as NOMEX (aramid fabric). The NOMEX restrains the radial expansion of the silicone tube, while permitting axial expansion thereof. However, in order to accomplish this result, the surround NOMEX is in a pleated condition when the inner tube is in its relaxed, unexpanded condition.
In the past, it has been necessary to manually pleat the NOMEX about a central silicone rubber tube. This has been done by workers who successively engage and shift small portions of the NOMEX to create the desired pleated condition. This is an arduous, time-consuming task, made more difficult by the fact that the pleats must be very uniform in order to insure proper operation of the harness tubes. Generally, when manual pleating is done by an experienced worker, each tube takes at least about 15–20 minutes to complete.
Mechanical pleating devices have been proposed in the past, but none are suited for pleating of tubular bodies such as flexible NOMEX. For example, U.S. Pat. No. 3,343,220 describes an apparatus for corrugating and compressing flexible plastic tubing. In use, a flexible tube is circumferentially compressed through the use of pressurized air, whereupon a shiftable piston is employed to complete the pleat. This is an excessively complex mechanism which would be difficult to use efficiently. U.S. Pat. No. 3,012,604 describes and apparatus for pleating paper tubes. In this device, a feed pipe conveys a workpiece to a corrugating station where radially movable jaws operate on the workpiece to create pleats. U.S. Pat. No. 5,064,598 describes a pleating device used to pleat continuous web materials in order to create filter inserts. Finally, U.S. U.S. Pat. Nos. 5,510,071, 5,560,941, 5,522,718, and 5,372,774 are all directed to devices for the production of rigid corrugated synthetic resin tubing.
There is accordingly a need in the art for a simplified apparatus designed for the rapid and efficient pleating of flexible tubular materials.